This R21 proposal is aimed at testing the in vivo anti-tumor activity of a series of novel apoptosis-inducing agents as part of our effort to develop new therapeutic agents against prostate cancer. Based on our study on the cyclooxygenase-2 (COX-2) inhibitor celecoxib, we have generated a series of derivatives that display high potency in eliciting apoptotic death in prostate cancer cells, while exerting no adverse effect on normal prostate epithelial cells. Our data indicate that these apoptotic agents trigger cell death via mechanisms distinctly different from that of conventional anti-cancer agents. First, these molecules down-regulate multiple signaling pathways essential to cell survival, including those mediated by Akt and ERK2. Second, they stimulate intracellular Ca2+ increase by blocking endoplasmic reticulum (ER) Cat+-ATPases, a mechanism reminiscent of thapsigargin. This Ca2+ perturbing effect is noteworthy considering the crucial role of Ca2+ in the induction of apoptosis in androgen-independent prostate cancer cells. Moreover, the triggering of apoptosis by these molecules is independent of androgen responsiveness and genetic lesions associated with advanced prostate cancer. Consequently, these apoptosis-inducing agents have translational potential to be developed into chemotherapeutic agents to stop prostate cancer progression or to treat metastatic prostate cancer. The in vivo effect will be evaluated with a panel of prostate cancer cell lines using two animal models that constitute the two specific aims of this proposal. The first specific aim will be to examine the apoptotic activity in vivo against xenograft tumors in nude mice. Human prostate cancer cells will be injected into the subcutaneous space of athymic male nude mice (Baltic, nu/nu). Anti-tumor activity of the test compounds is assessed by the prevention of tumor formation or by the delay in tumor growth of the treated group with respect to the doxorubicin-treated and vehicle-treated control groups. The second specific aim will be to examine the apoptotic activity in vivo in the subrenal capsule tumor model. Human prostate adenocarcinoma tissue fragments are implanted under the renal capsule of immunocompetent mice to assess the chemosensitivity to the test agents. The subrenal capsular space represents an ideal site for the delivery of nutrients and drugs, provides a rich vascular bed, and permits easy visualization of the xenografts, in situ. Together, these animal-- model studies will validate that the in vitro apoptosis-inducing effect of these compounds is relevant for tumor growth inhibition in vivo.